Fuels containing deposit-control additives



CONTAINING DEPGSIT CONTROL ADDITIV ES Robert Y. Heisler, Stanley R. Newman, and Kenneth L. Dille, Fishkill, and Norman Alpert, Poughkeepsie, N. Y., assignors to The Texas Company, New York, N. Y., a corporation of Delaware No Drawing. Application January 18, 1956 Serial No. 559,761

8 Claims. (Cl. 4470) This invention relates to hydrocarbon fuels containing a novel class of additives which reduce the deposit-forming tendency of hydrocarbon fuels. More specifically, this invention discloses that superior motor fuels are obtained by the addition of a minor amount of a mixed carbonic acid diester of an aliphatic alcohol and of a polyglycol monoether.

As automobile manufacturers annually raise the compression ratio of their automobile engines in the race for higher horsepower, the need becomes greater for gasolines which burn cleanly, that is have low depositforming tendencies. Engine deposits which find their origin in the fuel are primarily responsible for surface ignition phenomena such as preignition and octane requirement increase (ORI) which is the tendency of spark ignition engines in service to require higher octane fuels for proper performance. As a consequence, gasoline manufacturers have placed increasing stress on reducing the deposit-forming tendencies of their fuels and have resorted to various additives either to reduce the amount of deposits or to minimize their effects. The present invention involves the discovery that a particular class of mixed carbonic acid diesters are outstanding in controlling the deposit-forming tendencies of hydrocarbon fuels.

The improved hydrocarbon fuels of this invention contain a mixed carbonic acid diester of an aliphatic alcohol and of a polyglycol monoether of the general formula wherein R is a monovalent hydrocarbon radical containing 6 to 18 carbon atoms, R is a divalent aliphatic hydrocarbon radical containing 2 to 3 carbon atoms, R" is a monovalent aliphatic hydrocarbon radical containing 1 to 14 carbon atoms and n is an integer having a value of 3 to 15. The mixed carbonic acid diesters of an aliphatic alcohol and of a polyglycol monoether prescribed inthis invention, hereafter called mixed carbonic acid diesters, are effective deposit-control additives in concentrations as low as 0.01 volume percent, but concentrations of 0.04 to 0.3 volume percent are normally employed. There is no upper limit of concentration, but economic considerations dictate that concentrations less than 1.0 volume percent glycol carbonate ester be present in the fuel. In our copending application Serial No. 559,762, filed of even date, the mixed carbonic acid diesters used as fuel additives in this invention are claimed as novel chemical compounds and their mode of preparation is described in detail.

In general, the mixed carbonic acid diesters which inhibit the deposit-forming tendencies of hydrocarbon fuels are prepared by a series of reactions involving the reaction of phosgene with a hydroxy compound to a chloroformate which is subsequently reacted with another hydroxy compound. One reaction procedure inoctane requirement increase.

,44A50 Patented July 22, 1958 volves the formation of a chloroformate by reaction of phosgene with a polyglycol monoether and subsequent reaction of the chloroformate with an aliphatic alcohol in the presence of a hydrogen chloride acceptor such as pyridine or quinoline. An alternate reaction procedure involves formation of a chloroformate by reaction of an aliphatic alcohol with phosgene and subsequent reaction of the chloroformate with a polyglycol monoether in the presence of a hydrogen chloride acceptor.

The hydrocarbon fuels of this invention are characterized by low deposit-forming tendencies with the result that an engine operated therewith shows exceptionally clean intake system, combustion space, valves, ring belt area and injection system if a diesel engine. The low deposit level in the engine minimizes surface ignition in all its manifestations, mainly preignition and knock. In addition, the low deposit level reduces the engines Deposits on surfaces contacted by the lubricating oil, such as piston skirts and cylinder walls, are very markedly reduced.

The mixed carbonic acid diesters usable in the fuels of this invention are exemplified by the following: the carbonic acid diester of amyl alcohol and of pentaethylene glycol monodecylphenyl ether, the carbonic acid diester of ethyl alcohol and of pentapropylene glycol monooctylphenyl ether, the carbonic acid diester of lauryl alcohol and of pentaethylene glycol monoamylphenyl ether, the carbonic acid diester of methyl alcohol and of decaethylene glycol monolauryl ether, the carbonic acid diester of amyl alcohol and of octaethylene glycol monooctyl ether, the carbonic acid diester of octyl alcohol and of decapropylene glycol monohexyl ether, the carbonic acid diester of 2-ethylhexyl alcohol and of pentapropylene glycol monooctyl ether, the carbonic acid diester of myristyl alcohol and of pentaethylene glycol monoheptyl ether, and the carbonic acid diester of nonyl alcohol and of hexaethylene glycol monolauryl ether.

It is necessary for the mixed carbonic acid diesters to have the prescribed formula in order to operate effectively as deposit-control additives. As will be demonstrated later, related carbonates are ineffective as deposit-control additives. Carbonic acid esters such as di- (2-butoxyethoxyethyl) carbonate and allyl ricinoleyl carbonate are ineffective as deposit-control additives. The following conclusions can be made as to the requirements of the additive molecule for the production of a mixed carbonic acid diester having deposit-control properties: (1) the C -C polyalkylene oxide radical, that is the (OR),, radical, must contain at least 3 repeating units and preferably 4 to 10 units; (2) the hydrocarbon monoether radical may be an aliphatic or aryl in nature and should contain at least 6 to 18 carbon atoms and preferably 6 to 14 carbon atoms, and (3) the aliphatic hydrocarbon radical esterified with the carbonate radical should contain 1 to 14 carbon atoms and preferably 2 to 10 carbon atoms.

Mixed carbonic acid diesters are effective as depositcontrol additives in concentrations between 0.01 and 1.0 volume percent of the fuel. Generally, dirtier fuels having a high concentration of olefinic components require high concentrations of the additive Whereas cleaner burning premium fuels are improved with respect to depositforming characteristics by smaller concentrations of the additive. In general, dirtier gasolines require an additive concentration between 0.1 and 0.3 volume percent whereas clean-burning premium fuels only need an additive concentration between 0.01 and 0.08 volume percent. As indicated previously, there is no critical upper limit from a functional viewpoint but economics dictate that the additive concentration be less than 1 volume percent of the fuel.

The mixed carbonic acid diesters described in this invention are efiective in controlling deposits in hydrocarbon fuels having boiling points up to about 700 F., although benefits also result when they are added to fuels containing residual stocks of higher boiling point. The major application of the additive is in gasoline for automotive engines wherein fuel-derived engine deposits have become a particularly vexing problem. The deposit-forming properties of diesel fuels and fuels designed for use in jets and gas turbines are also improved by the mixed carbonic acid diesters of this invention. In diesel fuels the presence of the additive maintains the injection system and combustion zone in a clean condition. This is particularly important with the increasing use of the so-called economy diesel fuels, that is fuels having a high sulfur content or containing cracked or residual stocks. Mixed carbonic acid diesters find particular application in jet fuels used as a cooling medium prior to their consumption. A mixed carbonic acid diester-containing jet fuel is an excellent heat exchange medium since it is relatively free from deposits in the cooling system and burner nozzle where deposits cannot be tolerated.

The deposit-forming properties of both regular and premium gasolines, both of the leaded and of the nonleaded type, are improved by the presence of mixed carbonic acid diesters. Gasolines, as used in this invention, comprise hydrocarbon fuels having boiling points up to approximately 400 F.

The action of the additives in controlling the depositforming tendencies of motor fuel was demonstrated by a Modified Chevrolet Deposits Test-CRC FL2650. The laboratory engines are operated under the standard conditions of this test with the exception that crankcase oil temperatures were 10 F. lower, the water jacket temperatures were 5 F. lower, and the crankcases of the test engines were ventilated. These modifications are in every case in the direction of making the test more severe and are intended to simulate low temperature conditions wherein deposit formation is most pronounced. After the termination of each run, the engine is disassembled and its parts are evaluated by a merit system adapted from the CRCL-4-1252 test. This merit system involves visual examination of the engine part in question and their rating according to deposits by comparison with standards which have assigned ratings. For

example, a rating'of 10 on piston skirt designates a perfectly clean piston while a rating of zero represents the worst condition. Similarly, a rating of 100 on total engine deposits represents a perfectly clean engine, etc.

In the following table there is a comparison of the various carbonic acid diesters in high quality regular V grade gasoline comprising a mixture of thermal cracked stock, fluid catalytically cracked stock and straight run gasoline. Base Fuel A had an 87.0 ASTM Research octane rating, contained 2.90 ml. of TEL per gallon, had an API gravity of 58.0 and a boiling range between 106 F. and 396 F.; it was negative in the copper corrosion test and had an oxidation stability in the ASTM test of 530 minutes minimum. Base Fuel B had a 90.5 ASTM Research octane rating, contained 2.67 ml. of TEL per gallon, had an API gravity of 59.0, and a boiling range between 93 and 395 B; it Was negative in the copper corrosion test and had an oxidation stability of 445 minutes minimum in the ASTM test. The reference fuels also contained minor amounts of gasoline inhibitors, namely N,N'-disecondary butyl paraphenylenediamine, lecithin, and N,N'-disalicylidene-1,2-diaminopropane. In all the runs in the table the laboratory engines in the Chevrolet S-II test were lubricated with Advanced Custom Made Havoline, a heavy duty type oil meeting Supplement I requirements and manufactured by The Texas Company.

4 TABLE Engine cleanliness in the modified Chevrolet S-Il test Piston Total Skirt Engine Deposits Base Fuel A 0,... 4.8 76.1 Base Fuel A plus 0.1 volume percent of:

Carbonic acid diester of allyl alcohol and of a polyethylene glycol monolam-yl ether (av. mol Wt. 600) 6.8 83. 8 Carbonic acid diester of allyl alcohol and of oentaethylcne glycol monooctylphenyl ether. 1 8. 2 88. 2 Carbonic acid diester of allyl alcohol and ricinoleyl alcohol 5. 2 79. 2 Diallyl ester of carbonic acid. 4. 8 75. 8 Base Fuel B 6. 0 79. 9 Base Fuel B plus 0.1 volume percent of:

Di (Z-butoxyethoxycthyl) carbonate- 5. 8 80. 8 Di-isooctyl carbonate 5. 7 81. 7

The data in the above table clearly show the effectiveness of mixed carbonic acid diesters of prescribed composition as deposit-contro-l additives for motor fuels. The fuels containing the carbonic acid diesters of aliphatic alcohols and polyglycol monoethers produce a much cleaner engine than the reference fuel. The piston skirt and total engine ratings of 8.2 and 88.2 respectively obtained with the fuel containing the carbonic diester of allyl alcohol and of pentaethylene glycol monocotylphenyl ether are better ratings than are obtained with some premium fuels. The ability of mixed carbonic acid diesters of prescribed composition to raise regular grade fuels to the engine cleanliness level of premium grade fuels indicates that the instant invention is a substantial step forward in solving the surface ignition problems encountered in high compression engines.

It is also significant that other carbonic acid diesters are relatively ineffective as deposit-control additives. Some of the carbonate diesters shown in the above table actually had a harmful effect on the deposit-forming properties of the fuel, While one, namely allyl ricinoleyl carbonate, caused only an insignificant improvement in the deposit-forming properties of the fuel.

An outstanding feature of the mixed carbonic acid diesters of this invention is that they do not possess any deleterious effect on other properties of the fuel. In many fuel additives, engine wear of parts such as piston rings, cylinder walls, bearings and valves, is a definite problem. Fuels containing mixed carbonic acid diesters of prescribed composition actually decrease engine wear under high temperature conditions.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. A normally liquid hydrocarbon fuel for internal combustion engines containing a carbonic acid diester of an aliphatic alcohol and of a polyglycol monoether of the following general formula R(OR' OCOOR" wherein R is a monovalent hydrocarbon radical containing 6 to 18 carbon atoms, R is a divalent aliphatic hydrocarbon radical containing 2 to 3 carbon atoms, R" is an aliphatic hydrocarbon radical containing 1 to 14 carbon atoms, and n has a value of 3 to 15, said carbonic acid diester being present in an amount sufficient to reduce the deposit-forming properties of said fuel.

2. A hydrocarbon fuel according to claim 1 containing 0.01 to 1.0 volume percent of said carbonic acid diester.

3. A hydrocarbon fuel according to claim 1 containing 0.04 to 0.3 volume percent of said carbonic acid diester.

4. A gasoline containing a carbonic acid diester of an aliphatic alcohol and of a polyglycol mono-ether of the general formula 5 wherein R is a monovalent hydrocarbon radical containing 6m 18 carbon atoms, R is a divalent aliphatic hydrocarbon radical containing 2 lo 3 carbon atoms, R" is an aliphatic hydrocarbon radicalcontaining l to 14 carbon atoms, and n has a value of 3 to 15, said carbonic acid diester being present in an amount sufiicient to reduce the deposit-forming properties of said gasoline.

5. A gasoline according to claim 4 containing 0.01 to 1.0 volume percent of said carbonic acid dicster.

6. A gasoline according to claim 4 containing 0.04 to 0.3 volume percent of said carbonic acid diester.

7. A gasoline containing 0.01-1.0 volume percent car- 6 bonic acid diester of allyl alcohol and of polyethylene glycol monolauryl ether (av. mol wt. 600).

8. A gasoline containing 0.01-1.0 volume percent carbonic acid diester of allyl alcohol and of pentaethylene glycol monooctylphenyl ether.

References Cited in the file of this patent UNITED STATES PATENTS 2,331,386 Gaylor Oct. 12, 1943 2,379,252 Muskat et a1 June 26, 1945 2,651,657 Mikeska et a1. Sept. 8, 1953 2 ,789,891 Brandes et a1 Apr. 23, 1957 

1. A NORMALLY LIQUID HYDROCARBON FUEL FOR INTERNAL COMBUSTION ENGINES CONTAINING A CARBONIC ACID DIESTER OF AN ALIPHATILC ALCOHOL AND OF A POLYGLYCOL MONOETHER OF THE FOLLOWING GENERAL FORMULA 